coresight: platform: add OF/APCI dependency

When neither CONFIG_OF nor CONFIG_ACPI are set, we get a harmless
build warning:

drivers/hwtracing/coresight/coresight-platform.c:26:12: error: unused function 'coresight_alloc_conns'
      [-Werror,-Wunused-function]
static int coresight_alloc_conns(struct device *dev,
           ^
drivers/hwtracing/coresight/coresight-platform.c:46:1: error: unused function 'coresight_find_device_by_fwnode'
      [-Werror,-Wunused-function]
coresight_find_device_by_fwnode(struct fwnode_handle *fwnode)

As the code is useless in that configuration anyway, just add
a Kconfig dependency that only allows building when at least
one of the two is set.

This should not hinder compile-testing, as CONFIG_OF can be
enabled on any architecture.

Fixes: 20961aea ("coresight: platform: Use fwnode handle for device search")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/Kconfig

@@ -4,6 +4,7 @@
 #
 menuconfig CORESIGHT
 	bool "CoreSight Tracing Support"
+	depends on OF || ACPI
 	select ARM_AMBA
 	select PERF_EVENTS
 	help